Concerns were raised about the safety of windows on buses – which have the same type of windows as trams – eight years ago, after a fatal crash where a man was thrown from a bus in Croydon.

The Rail Accident Investigation Branch (RAIB) is currently investigating whether the type of glass in the windows of the tram which derailed at Sandilands Junction last November exacerbated injuries and led to the deaths of the seven victims.

Passengers with fatal or serious injuries had been "ejected or partially ejected", through broken windows and doors, the latest RAIB report found.

Caroline Pidgeon, a London Assembly member and chair of the transport committee at City Hall, has said if the RAIB concludes new standards regarding tram windows are needed, standards on London's 9,000 buses may need to be looked at.

She told the Advertiser: "Obviously the RAIB investigation into the Croydon tram crash that took place on November 9 is still not completed and we must await their final report and recommendations.

"However if they conclude that new standards of windows in trams are needed that might well mean we need to revisit the standards that exist in London's bus fleet of 9,000 vehicles.

"I would be surprised if lessons that apply to the tram network will not apply to London buses as well."

Nine years ago, 28-year-old Andrzej Karcz, from South Croydon, died after being thrown out of a side window of a double-decker bus when the driver, who was jailed for causing death by dangerous driving, crashed into the side of a tram in George Street at the junction with Park Lane.

The RAIB launched an investigation into the 2008 crash, but only made "learning points" and not full recommendations because it did not identify any lessons that would improve the tram network.

However, the learning points specifically raise concern over the safety of bus windows on the side of vehicles.

The report into the 2008 crash, published in January 2009, reads: "The RAIB has also noted that the side windows on the upper deck of the bus appeared to offer little protection to persons sitting on a front seat in case of a collision of this type.

"The RAIB has written to the Department for Transport (DfT) and the organisation who manages the bus services to express its concern."

Transport for London (TfL), which manages surface transport in the capital, has confirmed to the Advertiser that the same type of glass is used in both trams' and buses' windows.

This is toughened glass on the side windows, which shatters when subjected to a large impact, but safety laminated glass in the front which can crack on impact, but will stay in place because of plastic layers in the middle of the sheet.

TfL told the Advertiser earlier this year how it worked "closely" with the RAIB during the investigation into the 2008 tragedy.

A spokeswoman said: "We do everything possible to ensure the highest levels of safety for our customers and staff.

"At the time of the incident we worked closely with the RAIB to ensure that all necessary safety measures were being adhered to.

"This included reviewing the vehicle specifications of our bus fleet to make certain they incorporated the highest passenger safety standards.

"This review concluded that a redesign was not warranted.

"We continue to explore further enhancements and are developing a groundbreaking bus safety specification for London vehicles to make our services even safer."

Recovery efforts to remove the damaged tram from the scene (Image: SWNS)

TfL added that The Road Vehicles (Construction and Use) Regulations specify the type of glass that must be used for buses and trams.

The DfT monitors bus safety but said it is up to individual bus operators and local transport authorities to ensure buses meet the requirements.

In the latest RAIB report into the November 9 tram crash, the agency said it would be "understanding the behaviour" of tram windows and the standards that are applicable to windows.

It stated it would also be looking at the difference between standards applied to trams and those applied to buses and trains.

Last month, a TfL panel heard how the Croydon tram crash has helped shine a "spotlight" on safety standards across Transport for London (TfL) contracted services.

The Office of Rail and Road (ORR) is conducting an investigation into any breaches of health and safety while the British Transport Police (BTP) are holding a criminal probe into the tram driver, Alfred Dorris.

TfL is also holding its own independent investigation and has been urged to publish it as soon as possible.